The present invention relates to a resin coating pipe mostly used in a fuel filler pipe of an automobile or the like, and a manufacturing method thereof.
FIG. 7 is an perspective view showing a fuel tank and a fuel filler pipe of an automobile. The fuel tank 1 is located at a lower portion of a body of an automobile, and the fuel filler pipe 2 is installed so as to connect the fuel feed portion 3 provided at the body outside plate and the fuel tank 1. In the course of the fuel filler pipe 2, an elastic pipe 4 formed from an elastic material such as a rubber is connected, and by the elasticity of this elastic pipe 4, the error (difference) in the relative position of the fuel feed portion 3 and the fuel tank 1 or the vibration are arranged to be absorbed.
As a material of the fuel filler pipe 2, a material which is excellent in corrosion resistance such as a stainless pipe is preferable, but a stainless pipe is expensive and further, it is scarce of processability such as bending workability, and therefore, commonly, a pipe material made by performing surface treatment such as plating or cationic electro-deposition coating onto the surface of a steel pipe which is cheap and has a good workability, is used as a material of the fuel filler pipe 2. The steel pipe material like this is used such that after it has been subjected to bending processing or the like, a resin coating layer such as a layer of polyethylene is further formed on the surface thereof, and it is made to be a resin coating pipe so that the corrosion resistance thereof may greatly be raised.
As a forming method of a resin coating layer in a resin coating pipe like this, for example, there is such a method that after electrostatically attaching a powdered resin material onto the surface of a pipe material, the pipe material is heated so that the resin material may be melted to form the resin coating layer, or there is such a method that a powdered resin material is sprinkled and attached to a previously heated pipe material, and after that, further, the pipe material is heated to form a resin coating layer.
However, in any above mentioned method, the thickness of the resin coating film is thick (not less than 0.3 mm), and if this thick resin coating layer is applied even to the end potion of the fuel filler pipe 2, the insertion into the elastic pipe 4 becomes difficult, and therefore, it is necessary to mask the peripheral surface near the end portion of the fuel filler pipe 2 through a specified length so that the resin coating layer may not be formed.
Previously, it has been arranged that first, as shown in FIG. 8, the masking member 5 formed approximately in a cylindrical shape (like a cup) from a material such as a heat resistant rubber, is fitted onto the end portion of the pipe material 6, and next, as shown in FIG. 9, a powdered resin material is attached to the rest part of the surface of the pipe material 6 and is subjected to heat treatment to form a resin coating layer 7, and finally, the masking member 5 is removed to complete the fuel filler pipe 2, and as shown in FIG. 7 and FIGS. 9, 10, the portion which has been masked is inserted into the inside diameter portion of the elastic pipe 4 as an insertion portion 8.
However, after the insertion portion 8 of the fuel filler pipe 2 has been inserted into the inside diameter portion of the elastic pipe 4, it often occurs that the elastic pipe 4 is a little shifted in the direction of slipping off from the insertion portion 8 under the influence of the contraction phenomenon of the elastic pipe 4 itself, the running vibration of the vehicle, or the like, and consequently, as shown in FIG. 10, between the end portion of the resin coating layer 7 and the elastic pipe 4, a clearance C is produced. At this portion of the clearance C, the insertion portion 8 where the resin coating layer 7 is not formed (skin of the pipe material 6) is exposed to the outside, and further, water can easily enter into the clearance C, and consequently, the possibility that the fuel filler pipe 2 may suffer corrosion from the portion of the clearance C, has been high.
The present invention is made to solve this problem, and the object of the invention is to provide a resin coating pipe and manufacturing method thereof in which the occurrence of corrosion at the insertion portion can be prevented, and also to provide a fuel tank having a high durability and reliability against the corrosion at the insertion portion of the fuel filler pipe.
This object can be achieved according to the present invention by providing a resin coating pipe wherein a peripheral surface near an end portion of a pipe material is masked through a specified length, and a resin coating layer is formed on a rest portion of a surface of the pipe material, and the masked portion is made to be an insertion portion to be inserted tightly into an inside diameter portion of another fitting member, said resin coating layer has its end portion being pressurized, and at that portion, a resin connecting portion extending along the insertion portion and capable of being fitted into the inside diameter portion of said another fitting member together with the insertion portion, is formed.
According to the resin coating pipe described above, when the insertion portion of the resin coating pipe is inserted into the inside diameter portion of another fitting member, the resin connecting portion formed to the end portion of the resin coating layer is fitted into the inside diameter portion of another fitting member together with the insertion portion, so that the resin connecting portion may overlap another fitting member. Therefore, even if another fitting member moves a little in the direction of slipping off from the insertion portion of the resin coating pipe, the insertion portion to which the resin coating layer is not formed, is not exposed to the outside, so that the occurrence of corrosion in the insertion portion may be prevented.
Furthermore, the object of the invention can be achieved by providing a manufacturing method of a resin coating pipe which comprises a masking step to fit a masking member onto an end portion of a pipe material, said masking member is formed approximately in a cylindrical shape and has a mold work portion provided in an inside diameter portion on an inlet side thereof, a coating step to form a resin coating layer onto a rest portion of a surface of the pipe material, and a molding step to slide the masking member in the axial direction toward a portion onto which the resin coating layer is formed, so as to pressurize an end portion of the resin coating layer by the mold work portion of the masking member, and to form a resin connecting portion which extends along the insertion potion and is capable of being fitted into the inside diameter portion of another fitting portion together with the insertion portion.
According to the manufacturing method of a resin coating pipe mentioned above, by sliding the masking member toward the resin coating layer formed onto the pipe material, the mold work potion of the masking member is pressed onto the end portion of the resin coating layer, so that the resin connecting portion can uniformly and easily be formed through the whole circumference of the end portion of the resin coating layer, and consequently, the occurrence of corrosion at the insertion portion of the resin coating pipe can surely be prevented.
Moreover, the object of the invention can be achieved by providing a manufacturing method of a resin coating pipe which comprises a masking step to fit a masking member onto an end portion of a pipe material, said masking member is formed approximately in a cylindrical shape from an elastic material and has a press fit portion with an inside diameter to be fitted by pressurizing onto the periphery of the pipe material, a coating step to form a resin coating layer onto a rest portion of a surface of the pipe material, and a molding step to slide the masking member in the axial direction toward a portion onto which the resin coating layer is formed, so as to pressurize an end portion of the resin coating layer by allowing the press fit portion of the masking member run onto the end portion of the resin coating layer, and to form a resin connecting portion which extends along the insertion potion and is capable of being fitted into an inside diameter portion of another fitting portion together with the insertion portion.
According to the manufacturing method of a resin coating pipe mentioned above, by sliding the masking member toward the resin coating layer formed onto the pipe material, the end portion of the resin coating layer is pressurized and extended thinly by the press fit portion of the masking member, so that the resin connecting portion can thinly, uniformly, and easily be formed through the whole circumference of the end portion of the resin coating layer. With this method, since it is unnecessary to form a special shape to the press fit portion of the masking member, the shape of the masking member can be made to be simple.
Also, the object of the invention can be achieved by providing a fuel tank with resin coating pipe comprising a resin coating pipe of this invention as a fuel filler pipe.
According to the fuel tank with a resin coating pipe described above, since a resin coating pipe with a high corrosion resistance at the pipe connecting portion is applied as a fuel filler pipe, the durability and the reliability of the whole fuel tank are improved.